Typically, providers of energy or commodities such as electricity, natural gas, and water, etc., have the utmost interest in measuring consumer consumption of the energy or commodity. Measured consumer consumption is useful for ensuring accurate billing for consumed energy and also for planning for future energy production needs. These providers, in many situations electrical energy utilities, may wish to measure total accumulated consumer consumption for the respective delivered energy or commodity. Utilities may also want to know how much energy, or a magnitude of energy, are being consumed at certain specific times or what peak (or maximum) magnitude of energy was consumed during certain time periods, such as an hour, day, week, or month, for example. This kind of energy magnitude measurement is commonly referred to as a demand measurement. In an electricity context, for example, a consumer's cumulative electrical energy consumption is typically measured by electronic electricity measurement meters (or electricity meters or simply “meters”) in units of kilowatt hours (kWh) and the consumer's demand is typically measured in kilowatts (kW).
Electronic electricity meters are typically capable of measuring a demand of a consumer's electricity load, such as a residence, commercial equipment, or industrial equipment. Electricity meters may also be capable of providing an indication that a configurable demand threshold has been exceeded. This configurable demand threshold is typically a threshold for a “total” demand. A total demand is that demand value that represents a maximum, or peak, demand measured in a predetermined period of time, such as a day, week, or month, for example. Typically, the predetermined period of time for a total demand is a month, and as such, the total demand would be the highest measured demand in the month. Once the predetermined period of time ends, the total demand may be reset so that a new total demand for a next period of time may be determined. The configurable demand threshold represents a total demand value that is considered to be, usually by the utility, a maximum demand that the consumer's electricity load may consume without affecting the stability of the utility's electrical distribution system. For example, a consumer may be restricted by a tariff to a total demand of 25 kW.
It is common for utilities to assign designations to periods of time which fall somewhere within total demand periods, such as hours of a day, days of a week, or weeks of a month, etc., during which electricity is drawn from the utilities' electrical distribution system. These designated periods of time identify so-called time-of-use periods or time-of-use tiers (TOU tiers). By way of example only, a period of time starting at midnight and ending at 5 am on a particular day of the week, Monday for example, may be designated as tier D. Also by way of example only, the period starting at 5 am Monday and ending at 8 am Monday may be designated as tier A. To continue the example for Monday, the period starting at 8 am and ending at 10 am may be designated as tier B, the period starting at 10 am and ending at 4 pm may be designated as tier A, the period starting at 4 pm and ending at 8 pm may be designated as tier B, and the period starting at 8 pm and ending at midnight Tuesday morning may be designated as tier C.
There could be additional time-of-use tier designations identifying additional and/or different time-of-use tier periods. Also, such time-of-use tiers may have different designation labels. Utilities may assign certain billing rates to respective time-of-use tiers (or TOU tiers, or simply “tiers”) to account for varying levels of burden to the utilities' electrical distribution systems as overall consumer demand for electricity tends to vary over the various TOU tiers. For example, consumers may pay more in tier B for the same amount of electrical energy consumed as that consumed in tier C. In addition, utilities may wish to know what the peak demand was for a particular TOU tier. The peak demand for a particular tier, or a time-of-use demand (or TOU demand), is something different from the total demand. As mentioned previously, the total demand represents a peak demand for a predetermined period of time such as a day, week, or month, whereas a time-of-use demand represents a peak demand for a designated period of time that falls within the period of time corresponding to the total demand. Accordingly, electricity meters may determine a time-of-use demand for the respective time-of-use tiers included within the total demand period of time.
Meters may also operate a load control that is integral to the meter, such as a switch or relay, in response to the consumer's electrical load exceeding a demand threshold (or register). The meter may set the relay or switch to cause some or all of the consumer's electrical load to become electrically de-energized. By doing so, the meter has effectively limited the demand consumed by the consumer's electricity load. The meter may electrically de-energize the electricity load directly through the integral load control. Or, the meter may electrically de-energize the electricity load with the integral load control indirectly via intermediate equipment, such as relays or switches external to the meter, for example.